The secondary light distribution lens for most of current LEDs are mainly smooth total reflection lens, the basic structure of which lies in that a smooth aspherical lens for converging light is positioned on top of a concave portion in the centre area, around which a smooth total reflection face is disposed. This lens mainly applies to the light distribution of a single-chip LED, which represents a circular and efficient light spot distribution. However, regarding the multi-chip LED, this lens may project such a light spot that forms square or petaline chip shadow due to image of the chip formed by the central aspherical face.